In order to purify automobile exhaust gases, honeycomb structures of conventional techniques are made of cordierite, SiC, or the like. Specifically, these honeycomb structures uses exhaust gas purifying catalysts. Such an exhaust gas purifying catalyst includes an inorganic binder carrying a promoter made of a ceria-zirconia solid solution or the like and a noble metal catalyst.
Recently, honeycomb structures made of a promoter component or the like have been under development. However, when honeycomb structures are constructed using a promoter component, there is a problem that the promoter particles are not completely bonded to each other and thus the strength of the honeycomb structure is insufficient. As measures against this, there are proposed honeycomb structures made of ceria particles, a ceramic material having lower self-sintering performance than ceria particles, and an inorganic binder (refer to PTL 1).